Piezoelectric MEMS resonant gas sensor for defence applications

Piezoelectric AIN resonators with high potential for gravimetric gas sensor application are reported in this paper. An array of interdigitated electrode fingers is used to excite plate acoustic Lamb waves within a piezoelectric layer. The resonant frequency can be changed by adjusting the size of electrode fingers and hence resonators with multiple frequencies from MHz to GHz can be fabricated on a single wafer. A 773.42 MHz resonator is coated with multiple layers of Polyelectrolyte multilayer (PEMs) in order to determine its sensitivity. The mass sensitivity of 4.75 Hz/fg, limit of detection (LOD) of 187.5 pg/mm², and the minimum detectable mass of 7.8 pg are measured.